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Conclusion: The results of this case series demon-trate that Avance nerve grafts can be successfully usedo reconstruct continuity defects of the lingual and infe-ior alveolar nerves. Five of seven patients who returnedor follow-up had some return of sensation. Advantageso using Avance nerve grafts include elimination of theecondary surgical site, secondary surgical site morbiditynd associated permanent sensory deficits as well asecreased operating time and controlled nerve sizeatch. Limitations of this initial case series include a

mall number of patients and limited follow-up. Futuretudies are necessary to compare Avance to primaryeurorrhaphy, autograft and conduits.

References

Krekoski, C.A., Neubauer, D., Zuo, J and Muir. Axonal Regenerationnto Acellular Nerve Grafts is Enhanced by Degradation of Chondroitinulfate Proteoglycan. J Neurosci, 21(16):6206-6213, 2001

Neubauer, D., Graham, J. and Muir, D. Chondroitinase Treatmentncreases the Effective Length of Acellular Nerve Grafts. Exp Neurol,07:163-170, 2007

Calvarial Defect in Mice as a Suitablenimal Model to Evaluate Wnt10begulated Bone Regeneration andineralization in Craniofacial Skeleton

ony Li, DDS, Pittsburgh, PA (Wang FM; Liu K;ostello BJ; Ouyang H)

resented by: Andrew Wargo, DMD, Pittsburgh, PA

Statement of the Problem: Skeletal defects areaused by a variety of etiological factors, including trauma,etabolic and genetic bone diseases, neoplasms, infection,

nd elective surgery. Examining signal transduction path-ays in bone development and metabolism has important

linical implications in the treatment of skeletal defects forral maxillofacial surgeons. Wnt proteins are secreted, lip-

d-modified glycoproteins that interact with cell surfaceeceptors to initiate a variety of biological processes, in-luding embryonic axis induction, specification of cell fate,nd renewal of stem cells. A number of studies have dem-nstrated that canonical Wnt signaling is a potent stimula-or for development of axial bones, via regulation of osteo-last proliferation and differentiation. It still remainsndecided if Wnt signaling regulates development andegeneration of craniofacial bones.

Materials and Methods: In this study, we used aenetic mouse model where Wnt10b, a canonical Wntrotein, is expressed from the promoter of osteocalcinOCN), a protein marker of mature osteoblasts. Com-ared with age and gender matched wild type (wt)nimals, the Wnt10b transgenic (tg) mice have enhancedone formation through the skeletal bones, thus recapit-lating the high bone mass phenotype in humans caused

y hyperactivation of Wnt signaling. First, we character- E

AOMS • 2009

zed osteogenesis of craniofacial bones. Using quantita-ive-PCR, we evaluated primary calvarial osteoblast dif-erentiation of both tg and wt animals by determiningRNA levels of key markers associated with mature

steoblasts, such as Runx2, OCN, alkaline phosphatase,nd type I collagen. Second, we examined collagen syn-hesis and deposition using trichrome staining. Third, wesed Von Kossa staining to determine calvarial boneiomineralization capacity. Lastly, we determined ifnt10b overexpression promotes regeneration and

one healing in skeletal defects by establishing a calvar-al defect in gender-matched 8-wk old tg and wt controlnimals. A partial thickness calvarial defect of 5 mmiameter was created using a slow speed round burith the midline corresponding to the saggital suture,

t the cross-section of the metopic and saggital su-ures. The size of calvarial defects was documentedmmediately post-op via �CT imaging. At 5 weeksostop, the animals again received �CT imaging. Theolume and diameter of residule defects were mea-ured via �CT analysis. Three dimensional reconstitu-ion of calvarial defects was achieved via GE Medicalystems Microview software.Methods of Data Analysis: We initially employed

ve pairs of animals for genetic analysis and histologicaltaining for collagen deposition and biomineralization.tudent t-test was employed to determine the statisticalignificance level for osteoblastic gene expression be-ween two genotypes. To evaluate the bone regenera-ion capacity of the tg and wt animals, one male and oneemale pair were initially included. Power analysis wassed to determine the appropriate size of the animalopulation for the regeneration study.Results: Compared with age- and gender-matchedild type animals, the Wnt10b transgenic mice dis-layed increased mRNA levels of Runx2, OCN, ALP andol-I, indicating enhanced osteoblastic differentiation. Inddition, they showed increased collagen synthesis, dep-sition, and biomineralization of craniofacial bones. Theesidual calvarial defects of tg mice were appreciablymaller than those in the wt control animals.

Conclusion: These results demonstrate that canoni-al Wnt signaling plays a critical role in regulating osteo-enesis of craniofacial bone and may promote boneegeneration of cranial bone defects. Initial results show

viable animal model for evaluating Wnt signaling inlucidating regenerrative pathways in skeletal defects. Inrder to substantiate initial findings, increased sampleize of animals will be part of future studies.

References

Krishnan, V., H.U. Bryant, and O.A. Macdougald, Regulation of boneass by Wnt signaling. J Clin Invest, 2006. 116(5): p. 1202-9Bennett, C.N., et al., Wnt10b Increases Postnatal Bone Formation by

nhancing Osteoblast Differentiation. J Bone Miner Res, 2007

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